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COLORADO SPRINGS, Colo. Results from a print-process study conducted in February 2006 by Universal SMT Laboratories (Binhamton, N.Y.) show that Photo Stencil's AMTX E-FAB stencil performed best out of 12 stencils tested, provided by five different stencil makers. The study isolated the stencil to determine performance differences among various stencils. Universal's study measured solder paste deposit height, area, and volume for more than 154,000 solder paste bricks; and used both lead-free and tin/lead solder paste. Paste volume and repeatability were measured for 16 SMT components in all 12 stencils. Stencils were ranked in paste-volume delivery performance and paste-volume repeatability.
Five electroform stencils and seven laser-cut stencils, including Photo Stencil's NicAlloy stencil, were studied. The company's AMTX E-FAB stencil was said to provide the best paste transfer for both solder pastes among stencils tested. Universal's yield-analysis program was used to determine the yield loss due to open defects of BGA and microBGA packages directly related to the stencil.
Results show that the increase in repair costs range from an additional $658 for the second-best tested stencil to $10,122 for the last-place stencil. The AMTX E-FAB stencil was shown to offer the lowest rework cost for tin/lead and lead-free solder pastes among all stencils tested. Photo Stencil's AMTX E-FAB stencil technology and manufacturing process was acquired from Xerox in 1998 for use in the SMT market. For a complete copy of Universal's report and two appendixes regarding physical properties of the stencils, please contact William Coleman, Ph.D., vice president of technology, Photo Stencil, at (719) 535-8528, or e-mail: firstname.lastname@example.org.